| Hi Gary, no it wasn't just you. The .001% I'm alluding to is the number of GA flight hours that involve fatalities. Statistically that is a sum of various failures including engine failures for whatever reason. So that would imply you want any one system to be quite a bit better than that.
Your point on sample size is well taken.
One really big problem with aviation electronics is that the total available market is so small. When I was working in commercial semiconductors we would do a test run of 80,000 chips to find the weak spots in the production process. ...then go back and tweak the physical layout and go to full production. You can't do that when your total lifetime market is in single digit thousands. You are part of the test run.
but if you want to talk about stats on ignition systems, suppose there are 2,000 units of a given system in the field and they have all flown 200 hours. If you talked to all 2,000 owners and only found 2 failures EVER that would be about in line with the safety goal. On the other hand if you've talked to only 10 of the 2,000 and 9 had failures and even if somehow you knew they were the only failures in the world, ever, you already have reason for concern.
Colyn On Oct 24, 2013, at 9:06 AM, Gary Casey wrote: I'm sure Colyn was referring to my experience with the Lightspeed (III) system that failed 3 times in less than 400 hours (I'm on my 4th one, making 3 failures, not 4, but I'll stay with 4 for the purpose of discussion). Regardless, 4 failures would have made for a per-hour failure rate of 1%, much, much worse than his .001% that he says is the fleet average. Okay, but the sample size is very small, making the statistic very weak. If we add one other plane to the statistic, another ES that I know of that has over 1,000 hours on dual Lightspeeds with no failures, the number now is 4 failures in 2,400 hours, or an hourly failure rate of 0.17%, 6 times "better." Still not good, but it illustrates the weakness of coming to a conclusion from such a small data
set. Gary
Colyn posted:
So to get to GA accident rates we as a fleet have
free of failures that
could contribute to a fatality (on all systems including the pilot) 99.999%
of the hours flown.
A system that fails 1% of the hours flown is about 1000 times more dangerous
than that.
Something to think about when selecting components.
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